Traditional data channel transmission techniques include for example, data channel multicasting, which may be employed in a digital subscriber line access multiplexer (DSLAM) network. A DSLAM network provides an end user, at a terminal or other endpoint, with the ability to switch between streams of data, or data channels, received from an upstream source. A DSLAM network is typically designed to accommodate a variety of different types of data channels, such as, for example, a number of video channels as well as channels associated with user data, voice and gaming traffic. The endpoints of a DSLAM platform are customer premises equipment (CPE) devices, which are commonly accessed by the network through modems at a residence or business. CPE devices may include, for example, televisions, computers, personal digital assistants (PDAs), telephones or other types of communication terminals. A DSLAM network enables the delivery of any of the available channels to an end user while simultaneously allowing the end user to use the data, voice and gaming channels.
An end user may select one data channel from a set of channels that are broadcasting at a given time. An Internet group multicast protocol (IGMP) signal has traditionally been used to effect this channel selection by sending an IGMP control message from the CPE device of the end user through the DSLAM network and to a broadband remote access server (B-RAS). The channel selection is conveyed upstream in order to effect the switch to a newly selected channel. Since the signal has to travel from the CPE device, and through the network to the B-RAS, the time required to effect the channel change is usually fairly long. In DSLAM applications utilizing a central office (CO), the CO in the network polls for IGMP control messages. A CO may support a large number of CPEs, thus, IGMP consolidation presents a significant challenge to the efficiency of the system.
Attempts to solve the problems of channel switching time and IGMP control message consolidation have resulted in the use of software controlled selective channel switching in an uplink card of the CO. In such attempts, channel switching time is reduced by receiving at the uplink card, those video channels considered popular, thereby anticipating end user requests. The channel switching speed between channels in this subset of popular channels is increased. However, the time required to join, or to switch to, channels that are not considered popular and have not been received at the uplink card, will remain fairly long. This is due to the fact that the IGMP control message for the unpopular channel travels back to the B-RAS so that the channel may be transmitted to and received at the uplink card of the CO.
These attempts also result in an additional delay within the CO. A line card in the CO sends the control message to the uplink card, which processes the control message. A delay occurs in this transmission due to the fact that a more complex switching is required in the CO instead of a simple broadcast of the data channels from the upstream equipment. Finally, IGMP control messages are also periodically generated from the CPE devices to ensure connectivity within the network. This connectivity check has the ability to flood the network with control messages.
Thus, a need remains for a technique that enables faster selection and switching of channels of a digital networking system, as well as a technique for decreasing the number of control messages sent over the network.